An intelligent photonic network (IPN) is considered to be a next generation network because of its capability to support potential unlimited bandwidth and its flexibility for dynamic network connectivity. Referring to FIG. 1, there is shown an example of an IPN network 100 in a meshed topology. As shown in FIG. 1, the network 100 comprises a plurality of access nodes 102, a plurality of edge nodes 104, and a plurality of core nodes 106. Each of the plurality of edge nodes 104 and each of the plurality of core nodes 106 comprises a router 108 and an optical cross-connect (OXC) 110. Each of the plurality of access nodes 102 is connected to a respective one of the plurality of edge nodes 104 by an optical fiber 112. Similarly, each of the plurality of edge nodes 104 is connected to at least one respective core node 106 by an optical fiber 112. Also, the core nodes 106 are connected by an optical fiber 112.
The network 100 may also be viewed logically having two planes. That is, as shown in FIG. 2, the network 100 may be viewed as having a data plane 202 and a control plane 204. The data plane 202, which comprises optical cross-connects (OXC) 110, performs data forwarding. The control plane 204, which comprises routers 108, is implemented with a set of intelligent protocols and handles all control messages.
With implemented intelligent protocols, the IPN network 100 is able to act like a circuit-switched network that is capable of handling network topology discovery, signal routing, wavelength path calculation and selection, wavelength path signaling and provisioning, failure detection and isolation, failure protection and restoration, network resource management, and so on, all dynamically. In this high-speed dynamic IPN network 100, failure protection and restoration under tight time constraints is a challenging problem. Failure restoration time is crucial to network performance in any protection and restoration scheme because long restoration time will cause data loss, which is not expected, especially in high-speed networks. On the one hand, a mechanism for failure protection and restoration is desirable because failures, such as fiber cuts or tragedy events, do occur in real networks. On the other hand, a protection and restoration mechanism should not become an obstacle for network capacity usage with full flexibility under normal conditions because the possibility of failure is very low in real networks. Consequently, two essential performance requirements for failure protection and restoration in photonic meshed networks become major challenges: 1) when a failure happens, the restoration time should be as short as possible; and 2) during normal network conditions, network capacity should be fully flexible for working path usage.
There are two common types of protection and restoration methods: reserved and unreserved, both having advantages and disadvantages. The key advantage of the reserved scheme is its speed because some alternative paths, called protection paths, are pre-calculated and allocated under normal network conditions to prevent failures that may happen sometime in future. This also brings a drawback of inefficient network capacity usage because there are always some capacities reserved ahead to prepare for possible future failures.
The unreserved scheme has an advantage of dynamically utilizing network capacity for working paths with full flexibility. In the unreserved scheme, spare capacity for failure restoration is also required, but it is not explicitly reserved in advance for any particular wavelength paths, though wavelength paths for restoration can be pre-calculated based on available capacity. A disadvantage of the unreserved scheme is its long restoration time because real-time signaling or re-dial is required in these schemes after failure detection and notification. Signaling should not be delayed by the switching speed of the data plane in a way that affects restoration time.
In view of the foregoing, it would be desirable to provide a technique for transmitting an optical signal through an optical network which overcomes the above-described inadequacies and shortcomings in an efficient and cost effective manner.